Did you change 100% of the gaskets and seals?? I just did this Friday it literally took me longer to replace all the gaskts and seals off the car then it did for me to pull the valve covers off then to change all the valve cover seals and bolt seals and my covers the two inner bolts (under the coil cover) were the worst offender of bad bolt seals, literally filled the spark plug hole with oil. For it to come out of your AC vents you must be gettting a lot of underhood smoke, I assume you are smelling it burning or seeing it outside as well??
2000 Jaguar XJR (Black with White Interior)
1964 Jaguar E-Type OTS 3.8
1962 Jaguar Mk. X 3.8
Jensen, MG, Austin, Mini, Mustang, Opel, Vauxhall, English Ford, Sunbeam, Hillman, Singer, among other Marques owned so please don't hesitate to ask for help if I can will be more than happy. `